1. Field of the Invention
The present invention relates to methods and systems for improving the transport of variable bit rate data signals over a bandwidth limited communication network.
2. Description of the Related Art
Numerous compression schemes address the transport and reconstruction of motion images (e.g. video) for pseudo-real-time and non-real-time applications. Many of these schemes make use of buffers, especially at a receiving end of a communication network, for storing partial blocks of information which are pre-transmitted to the receiver. For pseudo-real-time applications, the buffer has a buffer length which is a function of a total amount of bits of information to be sent and a bandwidth available in the communication network. For non-real-time applications, part of the information, such as Discrete Cosine Transform (DCT) coefficients, is sent ahead of time, while the rest of the information is sent later and reconstructed in real time.
The Motion Pictures Experts Group 2 (MPEG2) compression standard makes use of motion compensation to reduce the data rate. Although the content is compressed at a certain bit rate, such as 1.5 Megabits per second (Mbps), the actual bandwidth used temporally varies. The temporal variation creates peaks and troughs in the bandwidth. For purposes of illustration and example, consider a hypothetical real-time transmission of compressed motion images which produces a bit rate versus time graph 10 shown in FIG. 1. The bit rate has an upper bound of 6.5 Mbps and is variable over time. In a DVD movie, for example, the bit rate may vary from 2.5 Mbps to 8 Mbps.